Linq不明白哪里出来问题，请大家帮助分析一下.

[thinkc]

        private void simpleButton1_Click(object sender, EventArgs e)
        {
            List<TESTCLASS> list = new List<TESTCLASS>();
            int[] ary = new int[] { 1,1,1,1,2,2,2,3,3,3,4,4,4};

            for (int i = 0; i < 100; i++)
            {
                list.Add(new TESTCLASS(i, i));
            }

            var list2 = from t in list
                        select new TESTCLASS(t.X, t.Y);

            var list3 = from t in list2
                        join a in ary
                        on t.X equals a
                        select new { T = t, Order = a };

            //var list1 = list3.Select(p => p.T).Distinct();
            var list1 = list3.Select(p => p.T);
            foreach (var t in list1)
            {
                MessageBox.Show(list1.ToList().IndexOf(t).ToString() + list.IndexOf(t).ToString());
            }
        }

        public class TESTCLASS
        {
            public TESTCLASS(int x, int y)
            {
                this.x = x;
                this.y = y;
            }

            int x;
            public int X
            {
                get
                {
                    return x;
                }
                set
                {
                    x = value;
                }
            }

            int y;
            public int Y
            {
                get
                {
                    return y;
                }
                set
                {
                    y = value;
                }
            }
        }

为什么弹出的结果会是-1呀！

[Macosx]

加上这个
public class TESTCLASS : IEquatable<TESTCLASS>

public bool Equals(TESTCLASS other) {
return this.X == other.X && this.Y == other.Y;
}

[thinkc]

呵呵，这个我知道
我就想知道这里面究竟发生了什么？怎么会出现这种状况？

[Macosx]

默认比较是比对象的地址 而不是比内容

[以专业开发人员为伍]

linq确实相比过去写上一大片不太好调试。你应该断点跟踪每个查询结果（使用vs的watch窗口）。

[以专业开发人员为伍]

跟踪每个查询结果 => 跟踪每个查询语句

[thinkc]

代码有点问题，重新贴一下

        for (int i = 0; i < 100; i++)
            {
                list.Add(new TESTCLASS(i, i));
            }

            var list2 = from t in list
                        select new TESTCLASS(t.X, t.Y);

            foreach (var t in list2)
            {
                MessageBox.Show(list2.ToList().IndexOf(t).ToString());
            }

弹出对话框的值就是-1了,真的看不懂了，按理说不应该呀，我是从list2集合中判读list2中的对象呀

[thinkc]

完整代码

        private void simpleButton1_Click(object sender, EventArgs e)
        {
            List<TESTCLASS> list = new List<TESTCLASS>();
            int[] ary = new int[] { 1,1,1,1,2,2,2,3,3,3,4,4,4};

            for (int i = 0; i < 100; i++)
            {
                list.Add(new TESTCLASS(i, i));
            }

            var list2 = from t in list
                        select new TESTCLASS(t.X, t.Y);

            foreach (var t in list2)
            {
                while (true)
                {
                    MessageBox.Show(t.GetHashCode().ToString() + ":" + list2.ToList()[0].GetHashCode().ToString());
                    MessageBox.Show(list2.ToList().IndexOf(t).ToString());
                    return; ;
                }
            }

        }

        public class TESTCLASS
        {
            public TESTCLASS(int x, int y)
            {
                this.x = x;
                this.y = y;
            }

            int x;
            public int X
            {
                get
                {
                    return x;
                }
                set
                {
                    x = value;
                }
            }

            int y;
            public int Y
            {
                get
                {
                    return y;
                }
                set
                {
                    y = value;
                }
            }
        }

GetHashCode的值都不一样,真是见鬼了

[thinkc]

关键代码如果改成如下方式就可以了,先将将结果保存到一个集合中就可以了

            var list2 = from t in list
                        select new TESTCLASS(t.X, t.Y);
            var list3 = list2.ToList();
            foreach (var t in list3)
            {
                while (true)
                {
                    MessageBox.Show(t.GetHashCode().ToString() + ":" + list3.ToList()[0].GetHashCode().ToString());
                    MessageBox.Show(list3.ToList().IndexOf(t).ToString());
                    return; ;
                }
            }

那位大侠能就这个问题进行一下解释说明？